Unmanned space vehicles used for exploring outer space may have a mission life of many years. A dynamic isotope power system designed for use in such space vehicles provides electrical power for devices within the vehicle. A decaying nuclear material, such as plutonium oxide, gives off heat in this type of power system. The heat is used to heat a fluid such as toluene to vaporize it to drive a turbine which, in turn, drives an alternator to generate electrical power. A rotary fluid management device of a dynamic isotone power system comprises bearings which require lubrication with a filtered lubricant to avoid damaging the bearings. Because no maintenance is possible during the long mission in outer space, there is a problem of insuring that the lubricant filter not get clogged.
In-line filters large enough to preclude clogging during the many years of the space vehicle's mission would require bringing the lubrication flow out of the rotary fluid management device of the dynamic isotope power system, filtering it, and routing it back into the rotary fluid management device. However, such a filtering arrangement is disadvantageous in that it adds to the size, weight and complexity of the power system. In-line filtering apparatus are, per se, known as shown in U.S. Pat. No. 4,580,912, for example.